Familial adenomatous polyposis and duodenal lymphoma: report of a case.

The occurrence of duodenal polyposis is well recognized in familial adenomatous polyposis. Lymphoid hyperplasia in association with familial adenomatous polyposis usually occurs in the terminal ileum, but it can occur in the duodenum and may be endoscopically difficult to distinguish from an adenoma. A case report is presented in which a 54-year-old male with familial adenomatous polyposis, who 20 years earlier had a subtotal colectomy and ileorectal anastomosis, presented with a large rectal villous tumor and was found to have a duodenal extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue. The role of lymphoid hyperplasia in the development of mucosa-associated lymphoid tissue lymphoma is discussed, as well as the issue of mucosa-associated lymphoid tissue lymphoma in familial adenomatous polyposis. In cases in which biopsies of polypoid lesions in patients with familial adenomatous polyposis show dense lymphoid aggregates, flow cytometry may assist in the diagnosis.